This invention relates to an apparatus for controlling an elevator system, and more particularly to an elevator control apparatus which enhances the riding quality of a cage in the operation of starting or stopping the cage.
FIG. 5 shows a magnet type brake which is assembled so as to be unitary with a hoist.
Brake levers 50 are normally kept urged in directions indicated by arrows A, by means of springs 51. In consequence, brake shoes 52 grasp a brake wheel 53 to restrain the rotation thereof. The brake wheel 53 is compled to a rotary shaft 54 directly coupled to an electric motor, thereby to restrain the rotation of the motor and, in turn, the travel of a cage.
In addition, cams 55 each of which is formed in the shape of the letter L turn in directions indicated by arrows B with the A-directional movements of the brake levers 50, thereby to push a plunger 56 upwards.
When a brake coil 57 is energized, the plunger 56 is attracted to descend. With the descent, the plunger 56 turns the cams 55 in directions C, thereby to turn the brake levers 50 in directions D against the springs 51. As the brake levers 50 are turned, the brake shoes 52 release the braked wheel 53. Owing to the release, the rotary shaft 54 is driven by the motor so as to move the cage up or down.
A prior-art example of an elevator control apparatus employing the above brake will be explained with reference to FIG. 6. In the figure, numeral 1 designates a three-phase power source, and numeral 2 designates an electromagnetic contactor which opens and closes an electric contact from the A.C. power source 1 and which has a normally-open contact 2a. A drive circuit 3 for driving the motor 4 is configured of thyristors or transistors, and the motor 4 rotates the rotary shaft 54 so as to drive the cage 62 for ascent or descent. Shown at numeral 9 is an electromagnetic contactor which feeds the brake coil 57 with the voltage of a power source 10, and which has a normally-open contact 9a. A control circuit 11 is actuated by the closure of a start command contact 12 to energize the electromagnetic contactors 2 and 9 and to operate the drive circuit 3. Symbol V.sub.B denotes the voltage of a control power source for the control circuit 11. A sheave 60 is coupled to the rotary shaft 54 and has a main cable 61 wound there around, thereby to drive the cage 62 and a counterweight 63 for the ascent and descent in well-bucket fashion.
The above control apparatus for an elevator system operates as follows: When a call has arisen in the elevator system, the start command contact 12 is closed, and the control circuit 11 is actuated to energize the electromagnetic contactors 2 and 9. Thus, the contacts 2a and 9a are closed to feed electric power to the drive circuit 3 and to energize the brake coil 57 by means of the power source 10. Further, the control circuit 11 sends an operation command to the drive circuit 3, aiming at the timing at which current flows through the brake coil 57 to attract the plunger 56 and to consequently release the braked wheel 53, whereupon the drive circuit 3 supplies the electric power to the motor 4 so as to generate a torque for rotation. Owing to the torque, the cage 62 is smoothly started to ascend or descend.
Meanwhile, a diode 58 and a resistor 59 constitute a protective circuit which is usually disposed in order to protect the terminals of the coil 57 from dielectric breakdown and the contact 9a from burnout when the brake current has been cut off by the opening of the contact 9a.
Besides, the deceleration and stop of the cage 62 are controlled by the control circuit 11 and the drive circuit 3 until the rotational speed of the motor 4 becomes almost zero. When the motor speed has become zero, the contact 9a of the electromagnetic contactor 9 is opened so that the braking forces of the magnet brake may act.
Since the prior-art brake control apparatus for the elevator system is constructed and operated as stated above, the timing at which the brake coil is energized or deenergized for starting or stopping the cage and the timing at which the braking forces of the brake are actually released or exerted differ for every kind of elevator system and every site of installation, depending upon the clamped degrees of the brake springs, etc. Therefore, in such a case where the timing at which the braking forces of the brake are actually released and the timing at which the motor generates the torque do not match in the starting mode or where the timing at which the motor is decelerated and stopped by any other electrical means and the timing at which the braking forces of the brake are actually exerted do not match in the stopping mode, the riding quality of the cage in the starting or stopping mode is sometimes spoild.